The signalling channel suggests that central banks use sterilized interventions in the foreign exchange market to convey information about future mone tary policy to the market. To date, this theory is not sufficiently supported by theoretical work that establishes the link between intervention signals and exchange rates. This paper develops a two country model of sterilized interventions. I argue that reputational effects cannot eliminate the credibility problem between central banks and the private sector and that agents will only partially use available information to form exchange rate expectations. Both partialcredibility and non-rational expectations reduce the effectiveness of interventions. (JEL Classifications: E52, F31, F41)